Ets transcription factors and human disease

Transcription factor EHF drives cholangiocarcinoma development through transcriptional activation of glioma-associated oncogene homolog 1 and chemokine CCL2

Cholangiocarcinoma (CCA) is characterized by rapid onset and high chance of metastasis. Therefore, identification of novel therapeutic targets is imperative. E26 transformation-specific homologous factor (EHF), a member of the E26 transformation-specific transcription factor family, plays a pivotal role in epithelial cell differentiation and cancer progression. However, its precise role in CCA remains unclear. In this study, through in vitro and in vivo experiments, we demonstrated that EHF plays a profound role in promoting CCA by transcriptional activation of glioma-associated oncogene homolog 1 (GLI1). Moreover, EHF significantly recruited and activated tumor-associated macrophages (TAMs) through the C-C motif chemokine 2/C-C chemokine receptor type 2 (CCL2/CCR2) axis, thereby remodeling the tumor microenvironment. In human CCA tissues, EHF expression was positively correlated with GLI1 and CCL2 expression, and patients with co-expression of EHF/GLI1 or EHF/CCL2 had the most adverse prognosis. Furthermore, the combination of the GLI1 inhibitor, GANT58, and CCR2 inhibitor, INCB3344, substantially reduced the occurrence of EHF-mediated CCA. In summary, our findings suggest that EHF is a potential prognostic biomarker for patients with CCA, while also advocating the therapeutic approach of combined targeting of GLI1 and CCL2/CCR2-TAMs to inhibit EHF-driven CCA development.

Integrative genomic analyses reveal putative cell type-specific targets of the Drosophila ets transcription factor Pointed

The Ets domain transcription factors direct diverse biological processes throughout all metazoans and are implicated in development as well as in tumor initiation, progression and metastasis. The Drosophila Ets transcription factor Pointed (Pnt) is the downstream effector of the Epidermal growth factor receptor (Egfr) pathway and is required for cell cycle progression, specification, and differentiation of most cell types in the larval eye disc. Despite its critical role in development, very few targets of Pnt have been reported previously. Here, we employed an integrated approach by combining genome-wide single cell and bulk data to identify putative cell type-specific Pnt targets. First, we used chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) to determine the genome-wide occupancy of Pnt in late larval eye discs. We identified enriched regions that mapped to an average of 6,941 genes, the vast majority of which are novel putative Pnt targets. Next, we integrated ChIP-seq data with two other larval eye single cell genomics datasets (scRNA-seq and snATAC-seq) to reveal 157 putative cell type-specific Pnt targets that may help mediate unique cell type responses upon Egfr-induced differentiation. Finally, our integrated data also predicts cell type-specific functional enhancers that were not reported previously. Together, our study provides a greatly expanded list of putative cell type-specific Pnt targets in the eye and is a resource for future studies that will allow mechanistic insights into complex developmental processes regulated by Egfr signaling.

ETV7 regulates breast cancer stem-like cell features by repressing IFN-response genes

Cancer stem cells (CSCs) represent a population of cells within the tumor able to drive tumorigenesis and known to be highly resistant to conventional chemotherapy and radiotherapy. In this work, we show a new role for ETV7, a transcriptional repressor member of the ETS family, in promoting breast cancer stem-like cells plasticity and resistance to chemo- and radiotherapy in breast cancer (BC) cells. We observed that MCF7 and T47D BC-derived cells stably over-expressing ETV7 showed reduced sensitivity to the chemotherapeutic drug 5-fluorouracil and to radiotherapy, accompanied by an adaptive proliferative behavior observed in different culture conditions. We further noticed that alteration of ETV7 expression could significantly affect the population of breast CSCs, measured by CD44⁺/CD24^low cell population and mammosphere formation efficiency. By transcriptome profiling, we identified a signature of Interferon-responsive genes significantly repressed in cells over-expressing ETV7, which could be responsible for the increase in the breast CSCs population, as this could be partially reverted by the treatment with IFN-β. Lastly, we show that the expression of the IFN-responsive genes repressed by ETV7 could have prognostic value in breast cancer, as low expression of these genes was associated with a worse prognosis. Therefore, we propose a novel role for ETV7 in breast cancer stem cells’ plasticity and associated resistance to conventional chemotherapy and radiotherapy, which involves the repression of a group of IFN-responsive genes, potentially reversible upon IFN-β treatment. We, therefore, suggest that an in-depth investigation of this mechanism could lead to novel breast CSCs targeted therapies and to the improvement of combinatorial regimens, possibly involving the therapeutic use of IFN-β, with the aim of avoiding resistance development and relapse in breast cancer.

Immune-related genes in tumor-specific CD4+ and CD8+ T cells in colon cancer

Background

Immune escape is an immunological mechanism underlying tumorigenesis, and T cells play an important role in this process. In this study, immune-related genes were evaluated in tumor-infiltrating CD4⁺ and CD8⁺ T cells in colon cancer.

Methods

ESTIMATE was used to calculate stromal and immune scores for tumor datasets downloaded from The Cancer Genome Atlas–Colon Cancer (COAD). Differentially expressed genes (DEGs) between samples with high and low stromal and immune scores were screened, followed by a functional enrichment analysis of the overlapping DEGs. The DEGs related to CD4⁺ and the CD8⁺ T cells were then screened. Predicted miRNA–mRNA and lncRNA–miRNA pairs were used to construct a competing endogenous RNA (ceRNA) network. Furthermore, chemical–gene interactions were predicted for genes in the ceRNA network. Kaplan–Meier survival curves were also plotted.

Results

In total, 83 stromal-related DEGs (5 up-regulated and 78 down-regulated) and 1270 immune-related DEGs (807 up-regulated and 293 down-regulated genes) were detected. The 79 overlapping DEGs were enriched for 39 biological process terms. Furthermore, 79 CD4⁺ T cell-related genes and 8 CD8⁺ T cell-related genes, such as ELK3, were screened. Additionally, ADAD1 and DLG3, related to CD4⁺ T cells, were significantly associated with the prognosis of patients with colon cancer. The chr22-38_28785274–29,006,793.1–miR-106a-5p-DDHD1 and chr22-38_28785274–29,006,793.1–miR-4319-GRHL1 axes obtained from CD4⁺ and CD8⁺ T cell-related ceRNAs were identified as candidates for further studies.

Conclusion

ELK3 is a candidate immune-related gene in colon cancer. The chr22-38_28785274–29,006,793.1–miR-106a-5p-DDHD1 and chr22-38_28785274–29,006,793.1–miR-4319-GRHL1 axes may be related to CD4⁺ and CD8⁺ T cell infiltration in colon cancer.

EGFR activates GDH1 transcription to promote glutamine metabolism through MEK/ERK/ELK1 pathway in glioblastoma

Cancer metabolism research has recently been revived and its focus expanded from glucose and the Warburg's effects on other nutrients, such as glutamine. The underlying mechanism of oncogenic alterations of glutaminolysis remains unclear. Genetic alterations of EGFR are observed in ~50% of glioblastoma (GBM) patients, and have been found to play important roles in the metabolic abnormalities of GBM. In this study, we found that glutamine metabolism was upregulated after EGFR activation in a GDH1 (glutamate dehydrogenase 1)-dependent manner. Knockdown of GDH1 significantly reduced the cell proliferation, colony formation and tumorigenesis abilities of glioblastoma cells. Furthermore, we showed that GDH1-mediated glutaminolysis was involved in EGF-promoted cell proliferation. EGFR triggered the phosphorylation of ELK1 at Ser 383 through activating MEK/ERK signaling. Phosphorylated ELK1 enriched in the promoter of GDH1 to activate the transcription of GDH1, which then promoted glutamine metabolism. In addition, EGFR activation did not accelerate glutaminolysis in ELK1 knockdown or ELK1 Ser383-mutated cells. Collectively, our findings indicate that EGFR phosphorylates ELK1 to activate GDH1 transcription and glutaminolysis through MEK/ERK pathway, providing new insight into oncogenic alterations of glutamine metabolism.

Computational characterization of the binding mode between oncoprotein Ets-1 and DNA-repair enzymes

The Ets-1 oncoprotein is a transcription factor that promotes target gene expression in specific biological processes. Typically, Ets-1 activity is low in healthy cells, but elevated levels of expression have been found in cancerous cells, specifically related to tumor progression. Like the vast majority of the cellular effectors, Ets-1 does not act alone but in association with partners. Given the important role that is attributed to Ets-1 in major human diseases, it is crucial to identify its partners and characterize their interactions. In this context, two DNA-repair enzymes, PARP-1 and DNA-PK, have been identified recently as interaction partners of Ets-1. We here identify their binding mode by means of protein docking. The results identify the interacting surface between Ets-1 and the two DNA-repair enzymes centered on the α-helix H1 of the ETS domain, leaving α-helix H3 available to bind DNA. The models highlight a hydrophobic patch on Ets-1 at the center of the interaction interface that includes three tryptophans (Trp338, Trp356, and Trp361). We rationalize the binding mode using a series of computational analyses, including alanine scanning, molecular dynamics simulation, and residue centrality analysis. Our study constitutes a first but important step in the characterization, at the molecular level, of the interaction between an oncoprotein and DNA-repair enzymes.

ELK1 is up-regulated by androgen in bladder cancer cells and promotes tumor progression

Little is known about biological significance of ELK1, a transcriptional factor that activates downstream targets including c-fos proto-oncogene, in bladder cancer. Recent preclinical evidence also suggests the involvement of androgen receptor (AR) signaling in bladder cancer progression. In this study, we aim to investigate the functions of ELK1 in bladder cancer growth and their regulation by AR signals. Immunohistochemistry in bladder tumor specimens showed that the levels of phospho-ELK1 (p-ELK1) expression were significantly elevated in urothelial neoplasms, compared with non-neoplastic urothelium tissues, and were also correlated with AR positivity. Patients with p-ELK1-positive non-muscle-invasive and muscle-invasive tumors had significantly higher risks for tumor recurrence and progression, respectively. In AR-positive bladder cancer cell lines, dihydrotestosterone treatment increased ELK1 expression (mRNA, protein) and its nuclear translocation, ELK1 transcriptional activity, and c-fos expression, which was restored by an anti-androgen hydroxyflutamide. ELK1 silencing via short hairpin RNA (shRNA) resulted in decreases in cell viability/colony formation, and cell migration/invasion as well as an increase in apoptosis. Importantly, ELK1 appears to require activated AR to regulate bladder cancer cell proliferation, but not cell migration. Androgen also failed to significantly induce AR transactivation in ELK1-knockdown cells. In accordance with our in vitro findings, ELK1-shRNA expression considerably retarded tumor formation as well as its growth in xenograft-bearing male mice. Our results suggest that ELK1 plays an important role in bladder tumorigenesis and cancer progression, which is further induced by AR activation. Accordingly, ELK1 inhibition, together with AR inactivation, has the potential of being a therapeutic approach for bladder cancer.

Epithelial cell fate in the nephron tubule is mediated by the ETS transcription factors etv5a and etv4 during zebrafish kidney development

Kidney development requires the differentiation and organization of discrete nephron epithelial lineages, yet the genetic and molecular pathways involved in these events remain poorly understood. The embryonic zebrafish kidney, or pronephros, provides a simple and useful model to study nephrogenesis. The pronephros is primarily comprised of two types of epithelial cells: transportive and multiciliated cells (MCCs). Transportive cells occupy distinct tubule segments and are characterized by the expression of various solute transporters, while MCCs function in fluid propulsion and are dispersed in a "salt-and-pepper" fashion within the tubule. Epithelial cell identity is reliant on interplay between the Notch signaling pathway and retinoic acid (RA) signaling, where RA promotes MCC fate by inhibiting Notch activity in renal progenitors, while Notch acts downstream to trigger transportive cell formation and block adoption of an MCC identity. Previous research has shown that the transcription factor ets variant 5a (etv5a), and its closely related ETS family members, are required for ciliogenesis in other zebrafish tissues. Here, we mapped etv5a expression to renal progenitors that occupy domains where MCCs later emerge. Thus, we hypothesized that etv5a is required for normal development of MCCs in the nephron. etv5a loss of function caused a decline of MCC number as indicated by the reduced frequency of cells that expressed the MCC-specific markers outer dense fiber of sperm tails 3b (odf3b) and centrin 4 (cetn4), where rescue experiments partially restored MCC incidence. Interestingly, deficiency of ets variant 4 (etv4), a related gene that is broadly expressed in the posterior mesoderm during somitogenesis stages, also led to reduced MCC numbers, which were further reduced by dual etv5a/4 deficiency, suggesting that both of these ETS factors are essential for MCC formation and that they also might have redundant activities. In epistatic studies, exogenous RA treatment expanded the etv5a domain within the renal progenitor field and RA inhibition blocked etv5a in this populace, indicating that etv5a acts downstream of RA. Additionally, treatment with exogenous RA partially rescued the reduced MCC phenotype after loss of etv5a. Further, abrogation of Notch with the small molecule inhibitor DAPT increased the renal progenitor etv5a expression domain as well as MCC density in etv5a deficient embryos, suggesting Notch acts upstream to inhibit etv5a. In contrast, etv4 levels in renal progenitors were unaffected by changes in RA or Notch signaling levels, suggesting a possible non-cell autonomous role during pronephros formation. Taken together, these findings have revealed new insights about the genetic mechanisms of epithelial cell development during nephrogenesis.

Elk-3 is a KLF4-regulated gene that modulates the phagocytosis of bacteria by macrophages

ETS family proteins play a role in immune responses. A unique member of this family, Elk-3, is a transcriptional repressor that regulates the expression of HO-1. Elk-3 is very sensitive to the effects of inflammatory mediators and is down-regulated by bacterial endotoxin (LPS). In the present study, exposure of mouse macrophages to Escherichia coli LPS resulted in decreased, full-length, and splice-variant isoforms of Elk-3. We isolated the Elk-3 promoter and demonstrated that LPS also decreased promoter activity. The Elk-3 promoter contains GC-rich regions that are putative binding sites for zinc-finger transcription factors, such as Sp1 and KLFs. Mutation of the GC-rich region from bp -613 to -603 blunted LPS-induced down-regulation of the Elk-3 promoter. Similar to the LPS response, coexpression of KLF4 led to repression of Elk-3 promoter activity, whereas coexpression of Sp1 increased activity. ChIP assays revealed that KLF4 binding to the Elk-3 promoter was increased by LPS exposure, and Sp1 binding was decreased. Thus, down-regulation of Elk-3 by bacterial LPS is regulated, in part, by the transcriptional repressor KLF4. Overexpression of Elk-3, in the presence of E. coli bacteria, resulted in decreased macrophage phagocytosis. To determine whether limited expression of HO-1 may contribute to this response, we exposed HO-1-deficient bone marrow-derived macrophages to E. coli and found a comparable reduction in bacterial phagocytosis. These data suggest that down-regulation of Elk-3 and the subsequent induction of HO-1 are important for macrophage function during the inflammatory response to infection.

Benzene-poly-carboxylic acid complex, a novel anti-cancer agent induces apoptosis in human breast cancer cells

Some cases of breast cancer are composed of clones of hormonal-independent growing cells, which do not respond to therapy. In the present study, the effect of Benzene-Poly-Carboxylic Acid Complex (BP-C1) on growth of human breast-cancer cells was tested. BP-C1 is a novel anti-cancer complex of benzene-poly-carboxylic acids with a very low concentration of cis-diammineplatinum (II) dichloride. Human breast cancer cells, MCF-7 and T47D, were used. Cell viability was detected by XTT assay and apoptosis was detected by Flow Cytometry and by annexin V/FITC/PI assay. Caspases were detected by western blot analysis and gene expression was measured by using the Applied Biosystems® TaqMan® Array Plates. The results showed that exposure of the cells to BP-C1 for 48 h, significantly (P<0.001) reduced cell viability, induced apoptosis and activated caspase 8 and caspace 9. Moreover, gene expression experiments indicated that BP-C1 increased the expression of pro-apoptotic genes (CASP8AP1, TNFRSF21, NFkB2, FADD, BCL10 and CASP8) and lowered the level of mRNA transcripts of inhibitory apoptotic genes (BCL2L11, BCL2L2 and XIAP. These findings may lead to the development of new therapeutic strategies for treatment of human cancer using BP-C1 analog.

The role of Ets2 transcription factor in the induction of microRNA-155 (miR-155) by lipopolysaccharide and its targeting by interleukin-10

MicroRNA-155 (miR-155) is highly expressed in many cancers such as B cell lymphomas and myeloid leukemia and inflammatory disorders such as rheumatoid arthritis, atopic dermatitis, and multiple sclerosis. The role of miR-155 as both a promoter of inflammation and an oncogenic agent provides a clear need for miR-155 itself to be stringently regulated. We therefore investigated the transcriptional regulation of miR-155 in response to the respective pro- and anti-inflammatory mediators LPS and IL-10. Bioinformatic analysis revealed Ets binding sites on the miR-155 promoter, and we found that Ets2 is critical for miR-155 induction by LPS. Truncation and mutational analysis of the miR-155 promoter confirmed the role of the Ets2 binding site proximal to the transcription start site for LPS responsiveness. We observed increased binding of Ets2 to the miR-155 promoter and Ets2 deficient mice displayed decreased induction of miR-155 in response to LPS. IL-10 inhibited the induction of Ets2 mRNA and protein by LPS, thereby decreasing Ets2 function on the pri-155 promoter. We have thus identified Ets2 as a key novel regulator in both the positive and negative control of miR-155 in the inflammatory response.

The transcription factor E74-like factor 4 suppresses differentiation of proliferating CD4+ T cells to the Th17 lineage

The differentiation of CD4(+) T cells into different Th lineages is driven by cytokine milieu in the priming site and the underlying transcriptional circuitry. Even though many positive regulators have been identified, it is not clear how this process is inhibited at transcriptional level. In this study, we report that the E-twenty six (ETS) transcription factor E74-like factor 4 (ELF4) suppresses the differentiation of Th17 cells both in vitro and in vivo. Culture of naive Elf4(-/-) CD4(+) T cells in the presence of IL-6 and TGF-β (or IL-6, IL-23, and IL-1β) resulted in increased numbers of IL-17A-positive cells compared with wild-type controls. In contrast, the differentiation to Th1, Th2, or regulatory T cells was largely unaffected by loss of ELF4. The increased expression of genes involved in Th17 differentiation observed in Elf4(-/-) CD4(+) T cells suggested that ELF4 controls their programming into the Th17 lineage rather than only IL-17A gene expression. Despite normal proliferation of naive CD4(+) T cells, loss of ELF4 lowered the requirement of IL-6 and TGF-β signaling for IL-17A induction in each cell division. ELF4 did not inhibit Th17 differentiation by promoting IL-2 production as proposed for another ETS transcription factor, ETS1. Elf4(-/-) mice showed increased numbers of Th17 cells in the lamina propria at steady state, in lymph nodes after immunization, and, most importantly, in the CNS following experimental autoimmune encephalomyelitis induction, contributing to the increased disease severity. Collectively, our findings suggest that ELF4 restrains Th17 differentiation in dividing CD4(+) T cells by regulating commitment to the Th17 differentiation program.

Prostate derived Ets transcription factor and Carcinoembryonic antigen related cell adhesion molecule 6 constitute a highly active oncogenic axis in breast cancer

We previously reported overexpression of Prostate derived Ets transcriptionfactor (PDEF) in breast cancer and its role in breast cancer progression, supportingPDEF as an attractive target in this cancer. The goal of this research was to identifyspecific PDEF induced molecules that, like PDEF, show overexpression in breast tumorsand a role in breast tumor progression. PDEF expression was down regulated byshRNA in MCF-7 human breast tumor cell line, and probes from PDEF down-regulatedand control MCF-7 cells were used to screen the HG-U133A human gene chips. Theseanalyses identified 1318 genes that were induced two-fold or higher by PDEF in MCF-7 cells. Further analysis of three of these genes, namely CEACAM6, S100A7 and B7-H4, in relation to PDEF in primary breast tumors showed that in 82% of ER+, 67%of Her2 overexpressing and 24% of triple-negative breast tumors both PDEF andCEACAM6 expression was elevated 10-fold or higher in comparison to normal breasttissue. Overall, 72% (94 of 131) of the primary breast tumors showed 10-fold orhigher expression of both PDEF and CEACAM6. In contrast, S100A7 and B7-H4 failedto show concordant elevated expression with PDEF in primary tumors. To determinethe significance of elevated PDEF and CEACAM6 expression to tumor phenotype, theirexpression was down regulated by specific siRNAs in human breast tumor cell lines. This resulted in the loss of viability of tumor cells in vitro, supporting an oncogenicrole for both PDEF and CEACAM6 in breast cancer. Together, these findings show thatPDEF-CEACAM6 is a highly active oncogenic axis in breast cancer and suggest thattargeting of these molecules should provide novel treatments for most breast cancerpatients.

Transcriptional control of cancer metastasis

Transcriptional regulation is an essential component of tumor progression and metastasis. During cancer progression, dysregulation of oncogenic or tumor-suppressive transcription factors (TFs), as well as master cell fate regulators and tumor microenvironment-induced factors, collectively influence multiple steps of the metastasis cascade, including local invasion, dissemination, and eventual colonization of the tumor to distant organs. Furthermore, epigenetic alterations in tumor cells, including DNA methylation, as well as activation or suppression of histone deacetylases (HDACs), histone acetyltransferases (HATs), and other chromatin-modifying enzymes, can further distort the transcriptional network to influence metastasis. We focus here on recent research advances in transcriptional control of metastasis and highlight the therapeutic potential of targeting such transcriptional regulatory networks.

Potential contribution of SIM2 and ETS2 functional polymorphisms in Down syndrome associated malignancies

Background

Proper expression and functioning of transcription factors (TFs) are essential for regulation of different traits and thus could be crucial for the development of complex diseases. Subjects with Down syndrome (DS) have a higher incidence of acute lymphoblastic leukemia (ALL) while solid tumors, like breast cancer (BC) and oral cancer (OC), show rare incidences. Triplication of the human chromosome 21 in DS is associated with altered genetic dosage of different TFs. V-ets erythroblastosis virus E26 oncogene homolog 2 (ETS2) and Single Minded 2 (SIM2) are two such TFs that regulate several downstream genes involved in developmental and neurological pathways. Here we studied functional genetic polymorphisms (fSNP) in ETS2 and SIM2 encoding genes in a group of patients and control subjects to better understand association of these variants with DS phenotypes.

Methods

We employed an in silico approach to identify potential target pathways of ETS2 and SIM2. fSNPs in genes encoding for these two TFs were identified using available databases. Selected sites were genotyped in individuals with DS, their parents, ALL, BC, OC as well as ethnically matched control individuals. We further analyzed these data by population-based statistical methods.

Results

Allelic/genotypic association analysis showed significant (P < 0.03) differences of rs2070530, rs1051476, rs11254, rs711 for DS subjects compared to control. rs711 also exhibited significantly different genotypic distribution pattern in parents of DS probands (P < 0.02) and BC patients (P < 0.02). Interaction analysis revealed independent main effect of rs711 in all the groups, while rs11254 exhibited independent main effect in DS subjects only. High entropy values were noticed for rs461155 in the solid tumor groups. Significant interactive effects of rs2070531 with rs1051475, rs1051476, rs11254 were observed in all the groups except DS.

Conclusions

We infer from the present investigation that the difference in frequencies of fSNPs and their independent as well as interactive effects may be the cause for altered expression of SIM2 and ETS2 in DS and malignant groups, which affects different downstream biological pathways. Thus, altered expression of SIM2 and ETS2 could be one of the reasons for variable occurrence of different malignant conditions in DS.

Purification, crystallization and preliminary X-ray crystallographic analysis of the ETS domain of human Ergp55 in complex with the cfos promoter DNA sequence

The Ergp55 protein belongs to the Ets family of transciption factors. The Ets transcription factors are involved in various developmental processes and the regulation of cancer metabolism. They contain a highly similar DNA-binding domain known as the ETS domain and have diverse functions in oncogenesis and physiology. The Ets transcription factors differ in their DNA-binding preference at the ETS site and the mechanisms by which they target genes are not clearly understood. To understand its DNA-binding mechanism, the ETS domain of Ergp55 was expressed and purified. The ETS domain was crystallized in the native form and in complex forms with DNA sequences from the E74 and cfos promoters. An X-ray diffraction data set was collected from an ETS-cfos DNA complex crystal at a wavelength of 0.9725 Å on the BM14 synchrotron beamline at the ESRF, France. The ETS-cfos DNA complex crystal belonged to space group C222(1), with four molecules in the asymmetric unit. For structure analysis, initial phases for the ETS-cfos DNA complex were obtained by the molecular-replacement technique with Phaser in the CCP4 suite using the coordinates of Fli-1 protein (PDB entry 1fli) and cfos DNA (PDB entry 1bc7) as search models. Structure analysis of the ETS-cfos DNA complex may possibly explain the DNA-binding specificity and its mechanism of interaction with the ETS domain of Ergp55.

Elf5 inhibits the epithelial-mesenchymal transition in mammary gland development and breast cancer metastasis by transcriptionally repressing Snail2

The epithelial-mesenchymal transition (EMT) is a complex process that occurs during organogenesis and in cancer metastasis. Despite recent progress, the molecular pathways connecting the physiological and pathological functions of EMT need to be better defined. Here we show that the transcription factor Elf5, a key regulator of mammary gland alveologenesis, controls EMT in both mammary gland development and metastasis. We uncovered this role for Elf5 through analyses of Elf5 conditional knockout animals, various in vitro and in vivo models of EMT and metastasis, an MMTV-neu transgenic model of mammary tumour progression and clinical breast cancer samples. Furthermore, we demonstrate that Elf5 suppresses EMT by directly repressing the transcription of Snail2, a master regulator of mammary stem cells and a known inducer of EMT. These findings establish Elf5 not only as a key cell lineage regulator during normal mammary gland development, but also as a suppressor of EMT and metastasis in breast cancer.

Transcriptional regulation of mouse PXR gene: an interplay of transregulatory factors

Pregnane X Receptor (PXR) is an important ligand-activated nuclear receptor functioning as a ‘master regulator’ of expression of phase I, phase II drug metabolizing enzymes, and members of the drug transporters. PXR is primarily expressed in hepatic tissues and to lesser extent in other non-hepatic tissues both in human and in mice. Although its expression profile is well studied but little is known about the regulatory mechanisms that govern PXR gene expression in these cells. In the present study, we have cloned and characterized over 5 kb (−4963 to +54) region lying upstream of mouse PXR transcription start site. Promoter-reporter assays revealed that the proximal promoter region of up to 1 kb is sufficient to support the expression of PXR in the mouse liver cell lines. It was evident that the 500 bp proximal promoter region contains active binding sites for Ets, Tcf, Ikarose and nuclear factor families of transcription factors. Electrophoretic mobility shift assays demonstrated that the minimal region of 134 bp PXR promoter was able to bind Ets-1 and β-catenin proteins. This result was further confirmed by chromatin immunoprecipitation analysis. In summary, the present study identified a promoter region of mouse PXR gene and the transregulatory factors responsible for PXR promoter activity. The results presented herein are expected to provide important cues to gain further insight into the regulatory mechanisms of PXR function.

Inhibitory effects of the transcription factor Ets-1 on the expression of type I collagen in TGF-β1-stimulated renal epithelial cells

Extracellular matrix (ECM) production and epithelial-mesenchymal transition (EMT) are important for phenotypic conversion in normal development and disease states such as tissue fibrosis. Transforming growth factor-β1 (TGFβ1) is one of the most potent inducers of ECM proteins, and its role in the pathogenesis of fibrosis is well established. Ets family is involved in a diverse array of biologic functions including cellular growth, migration, and differentiation. In the present study, we investigated whether Ets-1 has a role in ECM production and EMT in human renal tubuloepithelial cells (HKC cells). TGFβ1 treatment increases Ets-1 expression and nuclear translocation in the HKC cells. Overexpression of recombinant Ets-1 suppressed transcription of α2(I) collagen (COL1A2) and type I collagen production in the TGFβ1-activated HKC cells. From the experiments using specific inhibitors against Smad3 or mitogen-activated protein (MAP) kinase pathways, Ets-1 has an inhibitory role for COL1A2 transcription and the p38 MAPK pathway participates in the negative contribution of Ets-1 in TGFβ1/Smad3-activated renal cells.

[Regulation of human β-1,4-galactosyltransferase V gene expression in cancer cells]

β-1,4-Galactosyltransferase (β-1,4-GalT) V - whose human and mouse genes were cloned by us - has been suggested to be involved in the biosyntheses of N-glycans, O-glycans, and lactosylceramide by in vitro studies. Our recent study showed that β-1,4-GalT V-knockout mice are embryonic lethal, suggesting the importance of the glycans synthesized by β-1,4-GalT V for embryonic development. A subsequent study showed that murine β-1,4-GalT V is involved in the biosynthesis of lactosylceramide. It is well known that the glycosylation of cell surface glycoproteins and glycolipids changes dramatically upon the malignant transformation of cells. We found that among six β-1,4-GalTs the gene expression of only β-1,4-GalT V increases upon malignant transformation. The expression of the β-1,4-GalT V gene has been shown to be regulated by transcription factors Sp1 and Ets-1 in cancer cells. Both transcription factors regulate the gene expression levels of not only glycosyltransferases, but also key molecules involved in tumor growth, invasion and metastasis. Therefore, the abnormal glycosylation and malignant phenotypes of cancer cells are considered to be suppressed by regulating the expression levels of the transcription factor genes. This review gives a summary account of the gene discovery, in vivo function, and transcriptional mechanism of β-1,4-GalT V. Also, a perspective on applications of the manipulation of transcription factor genes to cancer therapy will be discussed.

The SAM domain of human TEL2 can abrogate transcriptional output from TEL1 (ETV-6) and ETS1/ETS2

Regulation of gene expression downstream of the Receptor Tyrosine Kinase signaling pathway in Drosophila relies on a transcriptional effector network featuring two conserved Ets family proteins, Yan and Pointed, known as TEL1 (ETV6) and ETS1/ETS2, respectively, in mammals. As in Drosophila, both TEL1 and ETS1/ETS2 operate as Ras pathway transcriptional effectors and misregulated activity of either factor has been implicated in many human leukemias and solid tumors. Providing essential regulation to the Drosophila network, direct interactions with the SAM domain protein Mae attenuate both Yan-mediated repression and PointedP2-mediated transcriptional activation. Given the critical contributions of Mae to the Drosophila circuitry, we investigated whether the human Ets factors TEL1 and ETS1/ETS2 could be subject to analogous regulation. Here we demonstrate that the SAM domain of human TEL2 can inhibit the transcriptional activities of ETS1/2 and TEL1. Drosophila Mae can also attenuate human ETS1/ETS2 function, suggesting there could be cross-species conservation of underlying mechanism. In contrast, Mae is not an effective inhibitor of TEL1, suggesting the mode of TEL2SAM-mediated inhibition of TEL1 may be distinct from how Drosophila Mae antagonizes Yan. Together our results reveal both further similarities and new differences between the mammalian and Drosophila networks and more broadly suggest that SAM domain-mediated interactions could provide an effective mechanism for modulating output from the TEL1 and ETS1/2 oncogenes.

Transcriptional regulation of miR-196b by ETS2 in gastric cancer cells

E26 transformation-specific sequence (ETS)-2 is a transcriptional modulator located on chromosome 21, alterations in its expression have been implicated with a reduced incidence of solid tumors in Down syndrome patients. MicroRNAs (miRNAs) are thought to participate in diverse biological functions; however, the regulation of miRNAs is not well characterized. Recently, we reported that miR-196b is highly expressed in gastric cancers. Herein, we demonstrate that miR-196b expression was significantly repressed by ETS2 during gastric cancer oncogenesis. We demonstrate that knockdown of endogenous ETS2 expression increases miR-196b expression. A genomic region between −751 and −824 bp upstream of the miR-196b transcriptional start site was found to be critical for the repression activity. This putative regulatory promoter region contains three potential ETS2-binding motifs. Mutations within the ETS2 binding sites blocked the repression activity of ETS2. Furthermore, knockdown of ETS2 or overexpression of miR-196b significantly induced migration and invasion in gastric cancer cells. In addition, alterations in ETS2 and miR-196b expression in gastric cancer cell lines affected the expression of epithelial–mesenchymal transition-related genes. The levels of vimentin, matrix metalloproteinase (MMP)-2 and MMP9 were drastically induced, but levels of E-cadherin were decreased in shETS2- or miR-196b-transfected cells. Our data indicate that ETS2 plays a key role in controlling the expression of miR-196b, and miR-196b may mediate the tumor suppressor effects of ETS2. We demonstrated that miR-196b was transcriptionally regulated by ETS2 and there was an inverse expression profile between miR-196b and ETS2 in clinical samples. This finding could be beneficial for the development of effective cancer diagnostic and alternative therapeutic strategies.

Transforming growth factor-β1 suppression of endotoxin-induced heme oxygenase-1 in macrophages involves activation of Smad2 and downregulation of Ets-2

Heme oxygenase (HO)-1 is a cytoprotective molecule that is induced during the response to injury. An increase in HO-1 is an acute indicator of inflammation, and early induction of HO-1 has been suggested to correlate with severity of injury. While a great deal is known about the induction of HO-1 by inflammatory mediators and bacterial lipopolysaccharide (LPS), much less is known about the effects of anti-inflammatory mediators on HO-1 expression. Transforming growth factor (TGF)-β is known to play a critical role in suppressing the immune response, and the TGF-β1 isoform is expressed in inflammatory cells. Thus, we wanted to investigate whether TGF-β1 could inhibit the expression of HO-1 during exposure to an inflammatory stimulus in macrophages. Here we demonstrate that TGF-β1 is able to downregulate LPS-induced HO-1 in mouse macrophages, and this reduction in HO-1 occurred through signaling of TGF-β1 via its type I receptor, and activation of Smad2. This TGF-β1 response is dependent on an intact Ets-binding site (EBS) located 93 base pairs upstream from the mouse HO-1 transcription start site. This EBS is known to be important for Ets-2 transactivation of HO-1 by LPS stimulation, and we show that TGF-β1 is able to suppress LPS-induced Ets-2 mRNA and protein levels in macrophages. Moreover, silencing of Smad2 is able to prevent the suppression of both HO-1 and Ets-2 by TGF-β1 during exposure to LPS. These data suggest that the return of HO-1 to basal levels during the resolution of an inflammatory response may involve its downregulation by anti-inflammatory mediators.

Molecular dynamics simulations and in silico peptide ligand screening of the Elk-1 ETS domain

BACKGROUND

The Elk-1 transcription factor is a member of a group of proteins called ternary complex factors, which serve as a paradigm for gene regulation in response to extracellular signals. Its deregulation has been linked to multiple human diseases including the development of tumours. The work herein aims to inform the design of potential peptidomimetic compounds that can inhibit the formation of the Elk-1 dimer, which is key to Elk-1 stability. We have conducted molecular dynamics simulations of the Elk-1 ETS domain followed by virtual screening.

RESULTS

We show the ETS dimerisation site undergoes conformational reorganisation at the α1β1 loop. Through exhaustive screening of di- and tri-peptide libraries against a collection of ETS domain conformations representing the dynamics of the loop, we identified a series of potential binders for the Elk-1 dimer interface. The di-peptides showed no particular preference toward the binding site; however, the tri-peptides made specific interactions with residues: Glu17, Gln18 and Arg49 that are pivotal to the dimer interface.

CONCLUSIONS

We have shown molecular dynamics simulations can be combined with virtual peptide screening to obtain an exhaustive docking protocol that incorporates dynamic fluctuations in a receptor. Based on our findings, we suggest experimental binding studies to be performed on the 12 SILE ranked tri-peptides as possible compounds for the design of inhibitors of Elk-1 dimerisation. It would also be reasonable to consider the score-ranked tri-peptides as a comparative test to establish whether peptide size is a determinant factor of binding to the ETS domain.

Preliminary crystallographic analysis of mouse Elf3 C-terminal DNA-binding domain in complex with type II TGF-beta receptor promoter DNA

Ets proteins are transcription factors that activate or repress the expression of genes that are involved in various biological processes, including cellular proliferation, differentiation, development, transformation and apoptosis. Like other Ets-family members, Elf3 functions as a sequence-specific DNA-binding transcriptional factor. A mouse Elf3 C-terminal fragment (amino-acid residues 269-371) containing the DNA-binding domain has been crystallized in complex with mouse type II TGF-beta receptor promoter (TbetaR-II) DNA. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 42.66, b = 52, c = 99.78 A, and diffracted to a resolution of 2.2 A.

Molecular events associated with epithelial to mesenchymal transition of nasopharyngeal carcinoma cells in the absence of Epstein-Barr virus genome

Epithelial-mesenchymal transition (EMT) is an important process in tumor metastasis. The EMT-related events associated with metastasis of NPC in the absence of EBV have not been elucidated. We established an EBV-negative NPC cell line from a bone marrow biopsy of an NPC patient. Using a Matrigel system we isolated an invasive and non-invasive sublines, designated NPC-BM29 and NPC-BM00. NPC-BM29 acquired an invasive-like phenotype characterized by EMT, marked by down-regulation of E-cadherin and β-catenin with concomitant increased expression of Ets1. NPC-BM29 cells expressed ≥ 10-fold higher of MMP-9 than NPC-BM00 cells. NPC-BM29 cells grew better in 2% serum than NPC-BM00 cells, with a population doubling-time of 26.8 h and 30.7 h, respectively. A marked reduction in colony-formation ability of NPC-BM00 cells compared to NPC-BM29 was observed. Wound-healing assay revealed that NPC-BM29 cells displayed higher motility than NPC-BM00 and the motility was further enhanced by cell treatment with TPA, a PKC activator. Cell surface markers and tumor-associated molecules, AE3, MAK6 and sialyl-Tn, were up-regulated in NPC-BM29 cells, whereas the expression of HLA-DR and CD54 was significantly increased in NPC-BM00 cells. NPC-BM29 consistently released higher levels of IL-8 and IL-10 than NPC-BM00, with low levels of IL-1α expression in both cell lines. Higher level of VEGF production was detected in NPC-BM00 than NPC-BM29 cells. These data show that EBV is not required for exhibiting multiple metastatic phenotypes associated with EMT. More studies that target right molecules/signalings associated with the EMT may offer new therapeutic intervention options for NPC invasion and metastasis.

Rapamycin-induced inhibition of HTLV-I LTR activity is rescued by c-Myb

Background

Rapamycin is an immunosuppressive which represses translation of transcripts harbouring a polypyrimidine motif downstream of the mRNA cap site through the mammalian target of rapamycin complex. It inhibits the abnormal autologous proliferation of T-cell clones containing a transcriptionally active human T-lymphotropic virus, type I (HTLV-I) provirus, generated from infected subjects. We showed previously that this effect is independent of the polypyrimidine motifs in the viral long terminal repeat (LTR) R region suggesting that HTLV-I transcription, and not translation, is being affected. Here we studied whether rapamycin is having an effect on a specific transcription factor pathway. Further, we investigated whether mRNAs encoding transcription factors involved in HTLV-I transcriptional activation, specifically CREB, Ets and c-Myb, are implicated in the rapamycin-sensitivity of the HTLV-I LTR.

Results

An in vitro analysis of the role of SRE- and NF-κB-mediated transcription highlighted the latter as rapamycin sensitive. Over-expression of c-Myb reversed the rapamycin effect.

Conclusion

The sensitivity of HTLV-I transcription to rapamycin may be effected through an NF-κB-pathway associated with the rapamycin-sensitive mTORC1 cellular signalling network.

Stromelysin-1 expression is activated in vivo by Ets-1 through palindromic head-to-head Ets binding sites present in the promoter

Regulation of the gene expression of Stromelysin-1 (matrix metalloproteinase-3), a member of the matrix metalloproteinase family, is critical for tissue homeostasis. The Stromelysin-1 promoter is known to be transactivated by Ets proteins through palindromic head-to-head Ets binding sites (EBS), an unusual configuration among metalloproteinase promoters. Patterns of increased co-expression of Stromelysin-1 and Ets-1 genes have been observed in pathological processes such as rheumatoid arthritis, glomerulonephritis and tumor invasion. In this context, we show in a synovial fibroblastic model cell line (HIG-82), which is able to co-express Stromelysin-1 and Ets-1, that the EBS palindrome is essential for the expression of Stromelysin-1. More precisely, using electrophoretic mobility shift assays, DNA affinity purification and chromatin immunoprecipitation, we demonstrate that endogenous Ets-1, but not Ets-2, is present on this palindrome. The use of a dominant-negative form of Ets-1 and the decrease of Ets-1 amount either by fumagillin, an antiangiogenic compound, or by short interfering RNA show that the activation rate of the promoter and the expression of Stromelysin-1 correlate with the level of endogenous Ets-1. Thus, it is the first demonstration, using this cellular model, that endogenously expressed Ets-1 is actually a main activator of the Stromelysin-1 promoter through its effective binding to the EBS palindrome.

The ternary complex factor Net regulates cell migration through inhibition of PAI-1 expression

Net, Elk-1, and Sap-1 are members of the ternary complex factor (TCF) subfamily of Ets transcription factors. They form ternary complexes with serum response factor (SRF) on serum response elements of immediate early genes such as c-fos and egr-1 and mediate responses to growth factors and mitogen-activated protein kinase signaling. Although the TCFs have been extensively studied as intermediates in signaling cascades, surprisingly little is known about their different target genes and physiological functions. We report that Net homozygous mutant mouse embryonic fibroblasts have a defect in cell migration. This defect results at least in part from increased expression of plasminogen activator inhibitor type 1 (PAI-1), a serine protease inhibitor (serpin) that controls extracellular proteolysis and cell matrix adhesion. The defect in cell migration can be reverted by the addition of a PAI-1 blocking antibody. Net represses PAI-1 promoter activity and binds to a specific region of the promoter containing Ets binding sites in the absence of SRF. We conclude that Net is a negative regulator of PAI-1 expression and is thereby involved in cell migration.

Function of the ETS transcription factor Yan in border cell migration

Invasive cell migration in both normal development and metastatic cancer is regulated by various signaling pathways, transcription factors and cell-adhesion molecules. The coordination between these activities in the context of cell migration is poorly understood. During Drosophila oogenesis, a small group of cells called border cells exit the follicular epithelium to perform a stereotypic, invasive migration. We find that the ETS transcription factor Yan is required for border cell migration and that Yan expression is spatiotemporally regulated as border cells migrate from the anterior pole of the egg chamber towards the nurse cell-oocyte boundary. Yan expression is dependent on inputs from the JAK/STAT, Notch and Receptor Tyrosine Kinase pathways in border cells. Mechanistically, Yan functions to modulate the turnover of DE-Cadherin-dependent adhesive complexes to facilitate border cell migration. Our results suggest that Yan acts as a pivotal link between signal transduction, cell adhesion and invasive cell migration in Drosophila border cells.

The novel ETS factor TEL2 cooperates with Myc in B lymphomagenesis

The human ETS family gene TEL2/ETV7 is highly homologous to TEL1/ETV6, a frequent target of chromosome translocations in human leukemia and specific solid tumors. Here we report that TEL2 augments the proliferation and survival of normal mouse B cells and dramatically accelerates lymphoma development in Emu-Myc transgenic mice. Nonetheless, inactivation of the p53 pathway was a hallmark of all TEL2/Emu-Myc lymphomas, indicating that TEL2 expression alone is insufficient to bypass this apoptotic checkpoint. Although TEL2 is infrequently up-regulated in human sporadic Burkitt's lymphoma, analysis of pediatric B-cell acute lymphocytic leukemia (B-ALL) samples showed increased coexpression of TEL2 and MYC and/or MYCN in over one-third of B-ALL patients. Therefore, TEL2 and MYC also appear to cooperate in provoking a cadre of human B-cell malignancies.

Ets1 is an effector of protein kinase Calpha in cancer cells

PKCalpha and Ets1 are both associated with breast cancer progression. Our previous studies suggested that these proteins are likely to functionally interact with one another. Here, we show that attenuation of endogenous PKCalpha expression (siPalpha) by RNA interference leads to reduced Ets1 protein expression in a variety of cancer cells. Pulse-chase experiments and treatment with proteasome inhibitor MG-132 revealed that siPalpha interferes with both Ets1 protein synthesis and stability. The effect of siPalpha on Ets1 expression could be partially prevented by KN-93, suggesting that calcium/calmodulin-dependent kinase II (CaMKII), a modulator of Ets1 activity, may play a role in PKCalpha-dependent Ets1 regulation. In contrast, Ets1-regulating kinases ERK1/2 were not found to be involved in this process. To assess the importance of the PKCalpha/Ets1 interaction, we compared the biological responses of MDA-MB-231 cells to PKCalpha- and Ets1-specific siRNAs (siE1). While only siPalpha induced changes in cellular morphology and anchorage-independent growth, both siRNAs similarly affected cellular responses to the antitumor drug mithramycin A and to UV light. Microarray analyses further showed that the expression of a certain set of genes was equally affected by siPalpha and siE1. The data suggest that Ets1 serves as an effector for PKCalpha to fulfil certain functions in cancer cells.

Des oncogènes à l’interface entre transcription et épissage

Oncogene activity ranges from transduction signals to transcription factors. Altered expression of oncogenes, either by chromosomal translocation, proviral insertion or point mutations, can lead to tumor formation. More specifically, data accumulated through the last two decades have shown that disregulation of oncogenic transcription factors can interfere with regulatory cascades that control the growth, differentiation, and survival of normal cells. There is also evidence that alterations of oncogene activity are associated with pre-mRNA splicing defects. The insights gained from the pivotal role of RNA polymerase II in coupling transcription and splicing have instigated a new line of research regarding the possible role of oncogenic transcription factors in pre-mRNA splicing regulation. This review focuses on recent advances addressing this question. Understanding the impact of alterations in the expression and/or function of oncogenes have important prognostic implications that can guide the design of new therapeutic drugs to promote differentiation and/or apoptosis over cell proliferation.

TEL2, an ETS factor expressed in human leukemia, regulates monocytic differentiation of U937 Cells and blocks the inhibitory effect of TEL1 on ras-induced cellular transformation

TEL2 is a member of the ETS family of transcription factors, which is highly similar to TEL1/ETV6. It binds to DNA via the ETS domain and interacts with itself or TEL1 via the pointed domain. The expression of TEL2 in normal and leukemic hematopoietic cells suggests a role in hematopoietic development. In this article, we describe the role of TEL2 in hematopoietic differentiation and cellular transformation. Quantitative reverse transcription-PCR showed that the expression of TEL2 mRNA was down-regulated during monocytic differentiation of U937 and HL60 induced by 1,25-(OH)2 vitamin D3 and 12-O-tetradecanoylphorbol 13-acetate, respectively. Overexpression of TEL2 in U937 cells inhibited differentiation induced by vitamin D3. In contrast, overexpression of a TEL2 mutant lacking either the pointed domain or a functional ETS domain induced both differentiation of U937 cells and inhibited their growth in vitro and in vivo. In addition, these mutants blocked TEL2-mediated transcriptional repression of a synthetic promoter containing TEL2 binding sites. These data suggest that dominant-negative inhibition of TEL2 might cause differentiation. Quantitative reverse transcription-PCR demonstrated that TEL2 is expressed at higher level in some primary human leukemia samples than in normal bone marrow. Furthermore, overexpression of TEL2 in NIH3T3-UCLA cells blocked the inhibitory effect of TEL1 on Ras-induced cellular transformation. These results suggest that TEL2 may play an important role in hematopoiesis and oncogenesis.

ESX induces transformation and functional epithelial to mesenchymal transition in MCF-12A mammary epithelial cells

ESX is an epithelial-restricted member of a large family of transcription factors known as the Ets family. ESX expression has been shown to be correlated with Her2/neu proto-oncogene amplification in highly aggressive breast cancers and induced by Her2/neu in breast cell lines, but its role in tumorigenesis is unknown. Previously, we have shown that ESX enhances breast cell survival in colony-formation assays. In order to determine whether ESX can act as a transforming gene, we stably transfected MCF-12A human mammary epithelial cells with the ESX expression vector, pCGN2-HA-ESX. The MCF-12A cell line is immortalized, but nontransformed, and importantly, these cells fail to express endogenous ESX protein. We used pCGN2-HA-Ets-2 and pSVRas expression vectors as positive controls for transformation. Like HA-Ets-2 and V12-Ras, stable expression of ESX induced EGF-independent proliferation, serum-independent MAPK phosphorylation and growth in soft agar. Additionally, stable ESX expression conferred increased cell adhesion, motility and invasion in two-dimensional and transwell filter assays, and an epithelial to mesenchymal morphological transition. In three-dimensional cultures, parental and vector control (pCGN2) cells formed highly organized duct-like structures with evidence of cell polarity, ECM adhesion-dependent proliferation and cell survival, and lack of cellular invasion into surrounding matrix. Remarkably, the ESX stable cells formed solid, disorganized structures, with lack of cell polarity, loss of adhesion junctions and cytokeratin staining and loss of dependence on ECM adhesion for cell proliferation and survival. In addition, ESX cells invaded the surrounding matrix, indicative of a transformed and metastatic phenotype. Taken together, these data show that ESX expression alone confers a transformed and in vitro metastatic phenotype to otherwise normal MCF-12A cells.

Conformations and dynamics of Ets-1 ETS domain-DNA complexes

Molecular dynamics studies have been performed for 3.5 ns on the ETS domain of Ets-1 transcription factor bound to the 14-bp DNA, d(AGTGCCGGAAATGT), comprising the core sequence of high-affinity (GGAA), ETS-GGAA. In like manner, molecular dynamics simulations have been carried out for 3.9 ns on the mutant low-affinity core sequence, GGAG (ETS-GGAG). Analyses of the DNA backbone of ETS-GGAG show conformational interconversions from BI to BII substates. Also, crank shaft motions are noticed at the mutated nucleotide base pair step after 1500 ps of dynamics. The corresponding nucleotide of ETS-GGAA is characteristic of a BI conformation and no crank shaft motions are observed. The single mutation of ETS-GGAA to ETS-GGAG also results in variations of helical parameters and solvent-accessible surface area around the major and minor grooves of the DNA. The presence of water contacts during the entire simulation proximal to the fourth base pair step of core DNA sequence is a characteristic feature of ETS-GGAA. Such waters are more mobile in ETS-GGAG at 100 ps and distant after 1500 ps. Anticorrelated motions between certain amino acids of Ets-1 protein are predominant in ETS-GGAA but less so or absent in the mutant. These motions are reflected in the flexibility of amino acid residues of the protein backbone. We consider that these conformational features and water contacts are involved in stabilizing the hydrogen bond interactions between helix-3 residues of Ets-1 and DNA during the transcription process.

Mutual repression of transcriptional activation between the ETS-related factor ERG and estrogen receptor

Transcription factors are known to interact with each other to modulate their transcriptional activity. In this study, we found that the transcriptional activity of human Erg (one of the Ets family-transcription factors) was repressed by several nuclear receptors, including human estrogen receptor ERalpha, nonsteroid receptors and orphan receptors. Conversely, Erg inhibited ERalpha-dependent transcription. These reciprocal functional interactions extended to other nuclear receptors such as thyroid hormone and retinoic acid receptors, as well as to Fli1, an ERG-related ETS factor. Although similarly inhibited by overexpression of the orphan nuclear receptors ERR1 and RORalpha, ERG activity was unaffected by either REV-ERBalpha1 or COUP-TFII. The antagonism between ERG and ERalpha did not depend on DNA binding inhibition or direct protein-protein interactions. Repression of ERalpha-dependent transcription required the carboxyterminal and aminoterminal transactivation domains of Erg whereas the carboxyterminal AF-2 domain of ERalpha was necessary for repression of Erg activity. Reciprocal inhibition between Erg and ERalpha was not alleviated by overexpressing CBP, SRC-1 or RIP 140, three nuclear coactivator proteins. A negative cross-talk observed between Erg and ERalpha expands their potential range of regulation and may be relevant in vivo, particularly in endothelial, urogenital and cartilaginous tissues where both factors are expressed.

EDL/MAE regulates EGF-mediated induction by antagonizing Ets transcription factor Pointed

Inductive patterning mechanisms often use negative regulators to coordinate the effects and efficiency of induction. During Spitz EGF-mediated neuronal induction in the Drosophila compound eye and chordotonal organs, Spitz causes activation of Ras signaling in the induced cells, resulting in the activation of Ets transcription factor Pointed P2. We describe developmental roles of a novel negative regulator of Ras signaling, EDL/MAE, a protein with an Ets-specific Pointed domain but not an ETS DNA-binding domain. The loss of EDL/MAE function results in reduced number of photoreceptor neurons and chordotonal organs, suggesting a positive role in the induction by Spitz EGF. However, EDL/MAE functions as an antagonist of Pointed P2, by binding to its Pointed domain and abolishing its transcriptional activation function. Furthermore, edl/mae appears to be specifically expressed in cells with inducing ability. This suggests that inducing cells, which can respond to Spitz they themselves produce, must somehow prevent activation of Pointed P2. Indeed hyperactivation of Pointed P2 in inducing cells interferes with their inducing ability, resulting in the reduction in inducing ability. We propose that EDL/MAE blocks autocrine activation of Pointed P2 so that inducing cells remain induction-competent. Inhibition of inducing ability by Pointed probably represents a novel negative feedback system that can prevent uncontrolled spread of induction of similar cell fates.

The biology of the Ets1 proto-oncogene

The Ets1 proto-oncoprotein is a member of the Ets family of transcription factors that share a unique DNA binding domain, the Ets domain. The DNA binding activity of Ets1 is controlled by kinases and transcription factors. Some transcription factors, such as AML-1, regulate Ets1 by targeting its autoinhibitory module. Others, such as Pax-5, alter Ets1 DNA binding properties. Ets1 harbors two phosphorylation sites, threonine-38 and an array of serines within the exon VII domain. Phosphorylation of threonine-38 by ERK1/2 activates Ets1, whereas phosphorylation of the exon VII domain by CaMKII or MLCK inhibits Ets1 DNA binding activity. Ets1 is expressed by numerous cell types. In haemotopoietic cells, it contributes to the regulation of cellular differentiation. In a variety of other cells, including endothelial cells, vascular smooth muscle cells and epithelial cancer cells, Ets1 promotes invasive behavior. Regulation of MMP1, MMP3, MMP9 and uPA as well as of VEGF and VEGF receptor gene expression has been ascribed to Ets1. In tumors, Ets1 expression is indicative of poorer prognosis.

Sequence specific DNA binding of Ets-1 transcription factor: molecular dynamics study on the Ets domain--DNA complexes

Molecular dynamics (MD) simulations for Ets-1 ETS domain-DNA complexes were performed to investigate the mechanism of sequence-specific recognition of the GGAA DNA core by the ETS domain. Employing the crystal structure of the Ets-1 ETS domain-DNA complex as a starting structure we carried out MD simulations of: (i). the complex between Ets-1 ETS domain and a 14 base-pair DNA containing GGAA core sequence (ETS-GGAA); (ii). the complex between the ETS domain and a DNA having single base-pair mutation, GGAG sequence (ETS-GGAG); and (iii). the 14 base-pair DNA alone (GGAA). Comparative analyses of the MD structures of ETS-GGAA and ETS-GGAG reveal that the DNA bending angles and the ETS domain-DNA phosphate interactions are similar in these complexes. These results support that the GGAA core sequence is distinguished from the mutated GGAG sequence by a direct readout mechanism in the Ets-1 ETS domain-DNA complex. Further analyses of the direct contacts in the interface between the helix-3 region of Ets-1 and the major groove of the core DNA sequence clearly show that the highly conserved arginine residues, Arg391 and Arg394, play a critical role in binding to the GGAA core sequence. These arginine residues make bidentate contacts with the nucleobases of GG dinucleotides in GGAA core sequence. In ETS-GGAA, the hydroxyl group of Tyr395 is hydrogen bonded to N7 nitrogen of A(3) (the third adenosine in the GGAA core), while the hydroxyl group makes a contact with N4 nitrogen of C(4') (the complementary nucleotide of the fourth guanosine G(4) in the GGAG sequence) in the ETS-GGAG complex. We have found that this difference in behavior of Tyr395 results in the relatively large motion of helix-3 in the ETS-GGAG complex, causing the collapse of bidentate contacts between Arg391/Arg394 and the GG dinucleotides in the GGAG sequence.

Ets2 and protein kinase C epsilon are important regulators of parathyroid hormone-related protein expression in MCF-7 breast cancer cells

Parathyroid hormone-related protein (PTHrP) promotes the metastatic potential and proliferation of breast cancer cells, and acts anti-apoptotically. In invasive MDA-MB-231 breast cancer cells, transforming growth factor beta-regulated PTHrP synthesis is mediated by an Ets1/Smad3-dependent activation of the PTHrP P3 promoter. In the present study, we studied the regulation of PTHrP expression in non-invasive, Ets1-deficient and transforming growth factor beta-resistant MCF-7 cells. We found PMA to be a strong stimulator of P3-dependent PTHrP expression in MCF-7 cells. Mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK) kinase 1 (MEK-1)/ERK1/2 inhibitor PD98059 interfered with this activity. Promoter studies revealed that the PMA effect depended on the Ets and stimulating protein-1 (Sp1)-binding sites. Of several Ets factors tested, Ets2, but not Ese-1, Elf-1 or Ets1, supported the PMA-dependent increase in promoter activity. PD98059 and a threonine to alanine mutation of the ERK1/2-responsive Ets2 phosphorylation site at position 72 inhibited the Ets2/PMA effect. Activated protein kinase C (PKC) epsilon could mimic PMA by stimulating the P3 promoter alone or in co-operation with Ets2 in an MEK-1/ERK1/2-dependent manner. Activated PKC alpha, although capable of co-operating with Ets2, failed to induce transcription from the P3 promoter on its own. The Ets2/PKalpha synergistic effect was neither sensitive to PD98059 nor to Thr(72)/Ala(72) mutation. PMA neither increased the expression of Sp1 nor modulated the transcriptional activity of Sp1. However, it induced the displacement of a yet unknown factor from the Sp1-binding site, which may result in Sp1 recruitment to the promoter. Our results suggest an ERK1/2-dependent Ets2/PKC epsilon synergism to be involved in PTHrP expression in MCF-7 breast cancer cells.

p62 overexpression in breast tumors and regulation by prostate-derived Ets factor in breast cancer cells

p62 is a multifunctional cytoplasmic protein able to noncovalently bind ubiquitin and several signaling proteins, suggesting a regulatory role connected to the ubiquitin-proteasome pathway. No studies to date have linked p62 protein expression with pathological states. Here we demonstrate the overabundance of p62 protein in malignant breast tissue relative to normal breast tissue. The proteasome inhibitor PSI increased p62 mRNA and protein; however, PSI treatment of breast epithelial cells transfected with the p62 promoter did not affect promoter activity. High levels of prostate-derived Ets factor (PDEF) mRNA have been identified in breast cancer compared to normal breast. Only the PSA and maspin promoters have been identified as targets of this transcription factor. Here we show that PDEF stimulates the p62 promoter through at least two sites, and likely acts as a coactivator. PSI treatment abrogates the PDEF-stimulated increase of p62 promoter activity by 50%. Thus, multiple mechanisms for the induction of p62 exist. We conclude that (1) p62 protein is overexpressed in breast cancer; (2) p62 mRNA and protein increase in response to PSI, with no change of basal promoter activity; (3) PDEF upregulates p62 promoter activity through at least two sites; and (4) PSI downregulates PDEF-induced p62 promoter activation through one of these sites.

Function of PEA3 Ets transcription factors in mammary gland development and oncogenesis

The Ets gene families of mice and man currently comprise 27 genes that encode sequence-specific transcription factors. Ets proteins share an approximately 85 amino acid structurally conserved ETS DNA binding domain. Genetic analyses in model organisms suggest roles for Ets proteins in embryonic development and various adult physiological processes. Chromosomal translocations involving several ETS genes are associated with Ewing's sarcomas and leukemias, whereas the overexpression of some ETS genes is linked with numerous malignancies, including breast cancer. Indeed PEA3, ETS-1, PDEF, and ELF-3 transcripts have all been reported to be elevated in human breast tumors. Some of the ETS genes that are overexpressed in human breast tumors are also overexpressed in mouse models of this disease. Notably, pea3, as well as its close paralogs er81 and erm, which comprise the pea3 subfamily of ets genes, are coordinately overexpressed in mouse mammary tumors. Genetic analyses in mice reveal required roles for one or more of the PEA3 subfamily Ets proteins in the initiation and progression of mouse mammary tumors. The pea3 subfamily genes are normally expressed in the primitive epithelium of mouse mammary buds during embryogenesis, and these three genes are expressed in epithelial progenitor cells during postnatal mammary gland development. Loss-of-function mutations in the mouse pea3 gene results in increased numbers of terminal end buds and an increased fraction of proliferating cells in these structures, suggesting a role for PEA3 in progenitor cell renewal or terminal differentiation. Taken together these observations suggest that the PEA3 subfamily proteins play key regulatory roles in both mammary gland development and oncogenesis.

Interfering with TGFbeta-induced Smad3 nuclear accumulation differentially affects TGFbeta-dependent gene expression

BACKGROUND

Transforming growth factor-beta (TGFbeta) plays an important role in late-stage carcinogenesis by stimulating invasive behavior of cancer cells, promoting neo-angiogenesis and by helping cancer cells to escape surveillance by the immune system. It also supports colonization of the bone by metastatic breast cancer cells by increasing expression of osteolytic parathyroid hormone-related protein (PTHrP). Interfering with TGFbeta signalling may thus weaken the malignant properties of cancer cells. We investigated to what extent two inhibitors, SB-202190 and SB-203580, interfere with TGFbeta-signalling in invasive MDA-MB-231 breast cancer cells. These compounds, formerly used as p38-MAPK-specific inhibitors, were recently also demonstrated to inhibit TGFbeta type I receptor kinase.

RESULTS

Our results show that these inhibitors delay the onset of TGFbeta-induced nuclear accumulation of Smad3 and reduces its amplitude. This effect was accompanied by a strong reduction in TGFbeta-responsivess of the slow-responder genes pthrp, pai-1 and upa, while the reactivity of the fast-responder gene smad7 to TGFbeta remained almost unchanged. Neither was the TGFbeta response of the fast-responder ese-1/esx gene, whose expression we found to be strongly downregulated by TGFbeta, affected by the inhibitors.

CONCLUSION

The data show that SB-202190 and SB-203580 suppress TGFbeta-dependent activation of genes that are important for the acquisition of invasive behavior, while having no effect on the expression of the natural TGFbeta inhibitor Smad7. This suggests that these compounds are potent inhibitors of malignant behavior of cancer cells.

CRM1-mediated nuclear export and regulated activity of the Receptor Tyrosine Kinase antagonist YAN require specific interactions with MAE

ETS family transcription factors serve as downstream effectors of signal transduction pathways, mediating cellular proliferation, differentiation and, when misregulated, tumorigenesis. The transcriptional repressor YAN prevents inappropriate responses to Receptor Tyrosine Kinase signaling by outcompeting POINTED for access to target gene promoters. We demonstrate that the molecular mechanism underlying downregulation of YAN involves CRM1-mediated nuclear export and define a novel role in this context for MAE, a co-factor previously implicated in facilitating MAPK phosphorylation of YAN. In addition to promoting YAN downregulation, MAE also participates in an inhibitory feedback loop that attenuates POINTED-P2 activation. Thus, we propose that MAE plays multiple independent roles in fine-tuning the levels of POINTED and YAN activity in accordance with changing RTK signaling conditions.

Identification and confirmation of a module of coexpressed genes

We synthesize a large gene expression data set using dbEST and UniGene. We use guilt-by-association (GBA) to analyze this data set and identify coexpressed genes. One module, or group of genes, was found to be coexpressed mainly in tissue extracted from breast and ovarian cancers, but also found in tissue from lung cancers, brain cancers, and bone marrow. This module contains at least six members that are believed to be involved in either transcritional regulation (PDEF, H2AFO, NUCKS) or the ubiquitin proteasome pathway (PSMD7, SQSTM1, FLJ10111). We confirm these observations of coexpression by real-time RT-PCR analysis of mRNA extracted from four model breast epithelial cell lines.

Human glycosaminoglycan glucuronyltransferase I gene and a related processed pseudogene: genomic structure, chromosomal mapping and characterization

Here we describe the characterization of the human glycosaminoglycan glucuronyltransferase I gene (GlcAT-I) and a related pseudogene. The GlcAT-I gene was localized to human chromosome 11q12-q13 by in situ hybridization of metaphase chromosomes. GlcAT-I spanned 7 kb of human genomic DNA and was divided into five exons. Northern blot analysis showed that GlcAT-I exhibited ubiquitous but markedly different expressions in the human tissues examined. The GlcAT-I promoter was approx. 3-fold more active in a melanoma cell line than in a hepatoma cell line, providing evidence for the differential regulation of the gene's expression. Stepwise 5' deletions of the promoter identified a strong enhancer element between -303 and -153 bp that included binding motifs for Ets, CREB (cAMP-response-element-binding protein) and STAT (signal transducers and activators of transcription). Screening of a human genomic library identified one additional distinct genomic clone containing an approx. 1.4 kb sequence region that shared an overall 95.3% nucleotide identity with exons 1-5 of GlcAT-I. However, a lack of intron sequences, as well as the presence of several nucleotide mutations, insertions and deletions that disrupted the potential GlcAT-I reading frame, suggested that the clone contained a processed pseudogene. The pseudogene was localized to chromosome 3. The human genome therefore contains two related GlcAT-I genes that are located on separate chromosomes.

Role of Ets transcription factors in mammary gland development and oncogenesis

PEA3 is the founding member of a subfamily of closely related ets genes that includes ER81 and ERM. PEA3 is expressed in the epithelial cells of mammary buds at the time that these first appear during mouse embryogenesis, and it is differentially expressed during postnatal mammary gland development. PEA3 expression is highest at the onset of puberty and during early pregnancy, times of extensive epithelial outgrowth and branching. PEA3 is expressed in undifferentiated epithelial cap cells of terminal end buds, and in differentiated myoepithelial cells of ducts and alveoli. Loss-of-function mutations in the PEA3 gene compromise mammary ductal branching at the onset of puberty and early during pregnancy. PEA3 is overexpressed in the vast majority of human breast tumors and in nearly all of the HER2-positive subclass of such tumors. PEA3 is similarly overexpressed in transgenic mouse models of this malignancy. Expression of dominant-negative PEA3 in the mouse mammary gland of MMTV-HER2 transgenic mice dramatically delays the onset and reduces the incidence of mammary tumors. Hence PEA3 and/or its close relatives play key regulatory roles in both mammary gland development and oncogenesis.

The Ets-transcription factor family in embryonic development: lessons from the amphibian and bird

This chapter reviews the expression and role of Ets-genes during embryogenesis of amphibians and birds. In addition to overlapping expression domains, some of them exhibit cell type-specific expression. Many of them are expressed in migratory cells: neural crest, endothelial, and pronephric duct cells for instance. They are also transcribed in embryonic areas affected by epithelio-mesenchymal transitions. Both processes involve modifications of cellular adhesion. Ets-family genes appear to coordinate changes in the expression of adhesion molecules and degradation of the extracellular matrix upon regulation of matrix metalloproteinases and their specific inhibitors. These functions are essential for physiological processes like tissue remodelling during embryogenesis or wound healing. Unfortunately they also play a harmful role in metastasis. Recent studies in the nervous system showed that Ets-genes contribute to the establishment of a cellular identity. This identity could rely on definite cell-surface determinants, among which cadherins could play an important role. In addition to cell-type specific expression, other factors contribute to the specificity of function of Ets-genes. These genes have a broad specificity of recognition of target sequences in gene promoters, insufficient for accurate control of gene expression. A fine tuning could arise from combinatorial interactions with other Ets- or accessory proteins.